Radiocarbon evidence for the importance of surface vegetation on fermentation and methanogenesis in contrasting types of boreal peatlands

Chanton, Jeffrey P.; Glaser, Paul H.; Chasar, L. S.; Burdige, David J.; Hines, Mark E.; Siegel, Donald I.; Tremblay, Lori Beth; Cooper, William T.

doi:10.1029/2008gb003274

Cited by 145 publications

(172 citation statements)

References 84 publications

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“…Whereas the solid-phase peat represents an important substrate for decomposition, a large proportion of CH 4 and CO 2 production uses materials in the dissolved phase (39). This is particularly true in fens due to fen DOM's high lability (relative to bog DOM), such that the majority of fen respiration products is derived from DOM decomposition (39).…”

Section: Discussionmentioning

confidence: 99%

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Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production

Hodgkins¹,

Tfaily²,

McCalley

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

288

362

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Carbon release due to permafrost thaw represents a potentially major positive climate change feedback. The magnitude of carbon loss and the proportion lost as methane (CH 4 ) vs. carbon dioxide (CO 2 ) depend on factors including temperature, mobilization of previously frozen carbon, hydrology, and changes in organic matter chemistry associated with environmental responses to thaw. While the first three of these effects are relatively well understood, the effect of organic matter chemistry remains largely unstudied. To address this gap, we examined the biogeochemistry of peat and dissolved organic matter (DOM) along a ∼40-y permafrost thaw progression from recently-to fully thawed sites in Stordalen Mire (68.35°N,19.05°E), a thawing peat plateau in northern Sweden. Thaw-induced subsidence and the resulting inundation along this progression led to succession in vegetation types accompanied by an evolution in organic matter chemistry. Peat C/N ratios decreased whereas humification rates increased, and DOM shifted toward lower molecular weight compounds with lower aromaticity, lower organic oxygen content, and more abundant microbially produced compounds. Corresponding changes in decomposition along this gradient included increasing CH 4 and CO 2 production potentials, higher relative CH 4 /CO 2 ratios, and a shift in CH 4 production pathway from CO 2 reduction to acetate cleavage. These results imply that subsidence and thermokarst-associated increases in organic matter lability cause shifts in biogeochemical processes toward faster decomposition with an increasing proportion of carbon released as CH 4 . This impact of permafrost thaw on organic matter chemistry could intensify the predicted climate feedbacks of increasing temperatures, permafrost carbon mobilization, and hydrologic changes.H igh-latitude soils in the Northern Hemisphere contain an estimated 1,400-1,850 petagrams (Pg) of carbon, of which ∼277 Pg is in peatlands within the permafrost zone (1, 2). This quantity of 277 Pg represents over one-third of the carbon stock in the atmosphere (ca. 800 Pg) (3). The fate of this carbon in a warming climate-i.e., the responses of net carbon balance and CH 4 emissions-is important in predicting climate feedbacks of permafrost thaw. Although northern peatlands are currently a net carbon sink, and have been since the end of the last glaciation, they are a net source of CH 4 (4, 5), emitting 0.046-0.09 Pg of carbon as CH 4 per year (4, 6, 7). Due to CH 4 's disproportionate global warming potential (33× CO 2 for 1 kg CH 4 vs. 1 kg CO 2 at a 100-y timescale) (8), this is equivalent to 6-12% of annual fossil fuel emissions of CO 2 (8.7 Pg of C) (9). The thaw of permafrost peatlands may alter their CH 4 and CO 2 emissions due to mobilization of formerly frozen carbon, higher temperatures, altered redox conditions, and evolving organic matter chemistry. Changes in carbon emissions, and in CH 4 emission in particular, could have potentially significant climate impacts. CH 4 is produced by two primary mechanisms (10-12),...

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Section: Discussionmentioning

confidence: 99%

“…This is particularly true in fens due to fen DOM's high lability (relative to bog DOM), such that the majority of fen respiration products is derived from DOM decomposition (39). We therefore analyzed DOM chemistry and reactivity in addition to peat chemistry and reactivity.…”

Section: Discussionmentioning

confidence: 99%

Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production

Hodgkins¹,

Tfaily²,

McCalley

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

288

362

View full text Add to dashboard Cite

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“…Previous studies of dissolved gases in peatlands have shown the CO 2 component to be older (Charman et al 1994), younger (Charman et al 1999), or essentially the same age (Aravena et al 1993;Chanton et al 2008) as the CH 4 component of dissolved gases. Our results are in agreement with the latter 2 studies in that the CO 2 component was either slightly younger, or the same age as the CH 4 component collected from the same depth.…”

Section: Field Experiments -Comparison With Other Studiesmentioning

confidence: 99%

“…This extra carbon cannot have been derived from dissolved organic carbon (DOC), which has been identified as one of the forms of carbon that may be transported in the peat profile (e.g. Aravena et al 1993), and is clearly a source for gases in peatlands (Chanton et al 2008), because although this process would lead to peat gases younger in age than the surrounding peat, it would not lead to CO 2 being younger than CH 4 at the same depth.…”

Section: Field Experiments -Comparison With Other Studiesmentioning

confidence: 99%

“…In North American fens and bogs, Chanton et al (2008) found that the 14 C concentrations of dissolved CO 2 and CH 4 were so similar that they suggested that analysis of 14 CO 2 alone could suffice as a proxy for 14 CH 4 . Chanton et al (2008) and Chasar et al (2000) found that both CO 2 and CH 4 were either similar in age to DOC, or intermediate between the age of DOC and the surrounding bulk peat, in contrast to the results of Clymo and Bryant (2008).…”

Section: Introductionmentioning

confidence: 99%

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Radiocarbon and Stable Carbon Analysis of Dissolved Methane and Carbon Dioxide from the Profile of a Raised Peat Bog

2011

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ABSTRACT. We developed and tested a new method to separate CO 2 and CH 4 from bulk gas samples for radiocarbon and stable-carbon analysis that utilizes a zeolite molecular sieve. To validate the technique, tests were performed using a suite of standard gases, composed of CO 2 and CH 4 of distinctly different isotopic composition. We employed the method to investigate the carbon isotopic composition of samples of dissolved CO 2 and CH 4 collected in situ from the near surface to deep layers of an ombrotrophic raised peat bog. Results showed that the age of both the CO 2 and CH 4 components of the dissolved gases increased with depth from ~0-300 BP at 0.25 m to ~4000 BP at 4 m. CH 4 was mainly similar or slightly older in age compared to CO 2 , with the greatest difference in ages occurring at 1 m depth where CH 4 was older by 430-615 yr. The  13 C values of CO 2 increased with depth from -12.4‰ and -8.0‰ at 0.25 m to +6.9‰ and +8.3‰ at 4 m, whereas the  13 C of CH 4 stayed in the range -58.4‰ to -70.6‰. The 14 C results from the deepest layers are consistent with a similar source for both gases. 14 C ages for the CO 2 component were younger compared to CH 4 , within the shallower depths of the peat bog (1 m) and demonstrate the incorporation of acrotelm-derived respired CO 2 into the catotelm.

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Surface production fuels deep heterotrophic respiration in northern peatlands

Corbett

Burdige

Tfaily

et al. 2013

Global Biogeochemical Cycles

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[1] Multiple analyses of dissolved organic carbon (DOC) from pore waters were conducted to define the processes that govern carbon balance in peatlands: (1) source, reactivity, and transport of DOC with respect to vegetation, peat, and age of carbon substrate, (2) reactivity of DOC with respect to molecular size, and (3) lability to photoxidation of surficial DOC. We found that surface organic production fuels heterotrophic respiration at depth in advection-dominated peatlands, especially in fens. Fen DOC was Δ 14 C enriched relative to the surrounding fen peat, and fen respiration products were similar to this enriched DOC indicating that DOC was the main microbial substrate. Bog DOC was more variable showing either enrichment in Δ 14 C at depth or Δ 14 C values that follow peat values. This variability in bogs is probably controlled by the relative importance of vertical transport of labile carbon substrates within the peat profile versus DOC production from bog peat. These results extended our set of observations to 10 years at one bog-fen pair and add two additional bog-fen pairs to our series of observations. Anaerobic incubations of peat, rinsed free of residual DOC, produced DOC and respiration products that were strikingly similar to the peat values in a bog and two fens. This result demonstrated conclusively that downward advection is the process responsible for the presence of modern DOC found at depth in the peat column. Fen DOC has lower C/N values and up to twice as much LMW (<1 kDa) DOC as bogs due to differences in organic inputs and greater microbial processing. Fluorescence irradiation experiments showed that fen DOC is more photolabile than bog DOC.

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Radiocarbon evidence for the importance of surface vegetation on fermentation and methanogenesis in contrasting types of boreal peatlands

Cited by 145 publications

References 84 publications

Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production

Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production

Radiocarbon and Stable Carbon Analysis of Dissolved Methane and Carbon Dioxide from the Profile of a Raised Peat Bog

Surface production fuels deep heterotrophic respiration in northern peatlands

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